About a Cerebral Cortex

Humans’ oversized brains could have evolved due to sexual selection. But what’s sexy about an
enlarged cerebral cortex? Women don’t say, "Look at the cerebral cortex on that dude! I want to
have his children!" Our ancestors must have instead been attracted to cerebral cortex behaviors.
Our cerebral cortexes enable many behaviors, e.g., speech and language. But what’s striking
about the cerebral cortex is how much of it is not dedicated to specific behaviors. The human
cerebral cortex has billions of general-purpose neurons, capable of learning any new idea. Why
were our ancestral mothers and fathers–unlike any other animals–sexually attracted to partners
who could learn new ideas?
Monogamy and Lying
Most nonhumanmammal fathers have little or no involvement with their offspring.12 Male gorillas
kill infants fathered by othermales. Male chimpanzees help all the youngsters in their group,
but they don’t know who fathered each child.
Human evolution may have begun when fathers helped raise their children, giving the children a
survival advantage. Among hunter-gatherers today, children without fathers are more than twice
as likely to die during childhood.
Monogamy could cause a conflict between two reproductive strategies. A man could try to have
sex with many women, risking rejection from women, violence from othermen, or his fatherless
children not surviving. Although initially more offspring might be conceived this way, such a
man might father no surviving children.
Or a man could choose to be in amonogamous relationship, and actively raise his children. Such
a man would father only a few children, but his children would likely survive and prosper.
A woman could have sex with a desirable (e.g., high-status, tall, strong, handsome)man, and risk
competing women taking him fromher. Or she could choose a stable, monogamous relationship
with a less-desirable man whom no one other woman wanted.
3.3.2 Sexual Lying Could Have Driven Cerebral Cortex Development
Getting caught reduces a liar’s reproductive success. Catching liars increases the lie-catcher’s
reproductive success.
Lying requires imagination, quick thinking, and, above all, thinking of new lies. Catching lies
requires imagination, quick thinking, and a longmemory.
Those are cerebral cortex activities. Effective liars also match their emotions to their lies. You
catch lies when an individual’s emotional state doesn’t match his or her words. Effective lying
requires integrating one’s cerebral cortex with one’s limbic brain.
A man or woman with a larger cerebral cortex, well-integrated with his or her limbic brain, is
better able to sexually lie, and to catch sexual lies. Such men and women became our ancestors.